TPI 350/T5 5spd FTW & prolly cheap. They never put the T5 behind the 5.7, but it will work & hold up pretty well for a daily driver. If you start gettin traction, or add more HP, it will be a different story. I ran one behind a 400 sbc in a '78 Grand Prix for many years & never had any problems. It ran high 13s & was driven daily for 6-7 years.
I have access to a T5 from a '84-'84 T/A. It is not the world class trans, but I didn’t run a world class trans behind my 400. It’ll work with pretty much any small block, too.
PM me if interested